copy paste formula to skip rows

[Guest]

Ok, so i have a basic return formula =(E31-E18-E28-E27)/E18 in cell E1208 and
it returns the value I'm looking for. Now what I'm trying to do is copy this
formula and paste it the cell below, E1209, however I need it to return the
formula of =(E44-E31-E41-E40). I can't seem to offset it every 13 rows and
need to formula that I can copy down quite a few times. Can nayone help??
Please advise...
Thank!!!

 

[Guest]

try this for your first formula, then copy it down

=(OFFSET(E$31,13*(ROW(A1)-1),0)-OFFSET(E$18,13*(ROW(A1)-1),0)-
SUM(OFFSET(E$27,13*(ROW(A1)-1),0,2,1)))/OFFSET(E$31,13*(ROW(A1)-1),0)